CAROLINA DUCK 71 



to have different preferences, and I never could tell which would turn out to be the 

 favored nests. 



As to size of opening, Heinroth considered eleven centimeters to be almost right 

 for the opening of the box, while he provided a depth of thirty to forty centimeters 

 and an inside diameter of at least twenty-one centimeters, using natural hollow logs 

 mostly. The narrowest opening used by wild birds seems to be about 3| inches and 

 in such narrow passages females have been known to crack the egg while still in the 

 oviduct (J.Dixon, 1924). Perhaps a safe size would be about 4 J by 4| inches (115mm.). 



One of the greatest troubles with Carolinas is the high percentage of infertile eggs 

 which are common to all hand-reared flocks. The same thing has even been recorded 

 in the wild (J. Dixon, 1924). Mr. Wormald once told me that 68% was the very 

 highest proportion of good eggs he ever got in any one year. Mr. Blaauw found 

 that 50% was about as good as his flock would do, and I think in the long run mine 

 averaged very little better. The proportion of sterile eggs varies a great deal from 

 year to year. 



Some fanciers have a deal of trouble in getting the newly hatched young to feed, 

 in other words, to "get them started growing." At one time Mr. H. K. Job had 

 whole broods that seemed all right when placed in the rearing coop but died without 

 even a chance. But the artificial rearing and handling of the young is a large subject 

 and one which has not really a proper place in a "natural" history, so that here I 

 shall have to leave it. 



In the London Gardens the average duration of life of eighty-five individuals was 

 only about three years, which seems to me very low indeed. Their oldest individual 

 lived nearly ten years (P. C. Mitchell, 1911). 



The food supplied to adult birds is usually the ordinary grains supplemented by 

 some green food from time to time and in the spring a little fish or meat. Instances 

 are on record of meat-hungry Carolinas confined in an aviary actually killing and 

 devouring small cage-birds such as canaries (U.S. Biological Survey records) ! 



The price of good stock is now about double what it used to be, $20.00 to $25.00 

 the pair, and even at that good birds are hard to obtain. I was told in Holland that 

 they are no longer reared there in anything like the numbers of former years. Yet I 

 feel sure that once a good strain is brought together, the fancier will come much 

 nearer to meeting expenses with this than he will with almost any other sort of duck. 

 I know that for several years my birds a good deal more than paid for themselves. 



Htbhids. I do not know that there are any instances of the taking of wild hybrids 

 between this and any other species. But in captivity this duck has often been crossed 

 with the Mallard, producing sterile progeny. Crosses with the European Widgeon, 

 Common Pochard, and Rosy-billed Duck also produced sterile hybrids (Heinroth, 

 1911; Poll, 1911). Grey informed me that he obtained young from the mating 



